This invention relates to vehicular warning systems for surface vehicles and, more particularly, to visual vehicular warning systems particularly suitable for use with lift trucks and the like.
Vehicle warning systems for lift trucks as used in warehouses and manufacturing plants are known and have been used in the art. One such system utilizes a warning lamp mounted on the lift truck itself, which lamp, in many arrangements, is electromechanically rotated to provide a more visible, and otherwise effective, visual indication. These warning systems are utilized to provide a visual indication to pedestrians and the like who many be endangered at the various intersections which are routinely traversed by the vehicles. Since these warning lamps are disposed directly on, and fixedly mounted to, the lift trucks, they are subjected to the various vehicle shocks and material handling vibrations. Accordingly, the lamps must be frequently replaced as the component lifetimes are relatively short due to the shocks and vibrations. Further, it has been found that the light intensity outputs of these vehicle-mounted lamps are often insufficient to command the attention of the pedestrains intended to be protected, particularly at blind intersections.
Another known vehicle warning system utilizes loop detectors in the form of a cable which provides a contact closure when the lift trucks cross thereover. The closure provided by the cable loops activates an external indicator device such as a bell, horn or light. These systems suffer from the disadvantages that the initial installation is quite expensive and the installations are restricted to only those areas which are amenable thereto. Further, these systems inherently present maintenance problems due to the continuous wear to which the loop detectors are continuously subjected.
Another known system for providing a vehicle presence warning comprises the use of mirror devices which must be mounted at elevated positions at the intersection in order to permit the lift trucks to pass thereunder while "permitting" the mirror device to be viewed from two or more blind directions. This system suffers from the known disadvantage that pedestrians tend to ignore these devices. That is, pedestrians have a natural tendency not to look in those directions or areas above them which therefore effectively defeats the function of such warning devices.
These and other disadvantages are overcome by the present invention wherein a visual vehicular warning system is provided which includes a sturdy, solid-state transmitter fixedly mounted to each vehicle. The system further includes a receiver at each protected intersection or location which responds to the signal provided by the vehicle-mounted transmitter. The output of the receiver controls an attention-demanding visual light output device.